Sculptor Atsuo Okamoto carves sculptures in granite – then cuts them into little pieces and MAILS them worldwide.

When they are returned years later, they have changed colour depending on where they’ve been.

Then he puts them back together again ... and calls them his TURTLES.

The 58 year-old artist, currently on a month-long visit to the Midlands, is one of Japan’s leading sculptors.

Born in Hiroshima, he has a studio just outside Tokyo, where he carves white granite from a quarry near his home, which he moves around his studio with the aid of a 50-tonne crane.

He then cuts his sculptures into small stones which he sends to collaborators in various countries to ‘look after’ – in an artistic take on the global Pet Rock craze of the 1970s.

One stone which had been lying on the ground in Cambodia came back chocolate brown, he reveals.

Another was green when it returned from Iceland.

The stones, which have all been numbered, are then reassembled into a patchwork sculpture.

On a visit to Birmingham, Atsuo explains: “I named it the Turtle Project because the stones go all over the world.

“It seems like a turtle, because a turtle is born and goes to the sea, then goes all over the world and comes back to the same place.

“For my first project, each stone had a number from one to 49. I started in 2001 and tried to find collaborators.

“It was very hard, because I had no contacts in Africa, for example. I set up a website, and that made things much easier.”

Since then, stones from Atsuo’s sculptures have been entrusted to people in countries including Germany, Greece, Pakistan, South Africa, Russia, Austria, China, the United States – and now Birmingham.

His collaborators send photographs of themselves with their stones, in one case posing in front of the president’s house in Islamabad.

Sometimes, though, things go wrong. A stone sent to Nigeria never returned because of the peculiarities of the Nigerian postal system.

But Atsuo is philosophical. Even a gap in a finished sculpture is part of its story, he explains.

“The director of the Brooklyn Museum was worried about losing the stone she had, because there are so many bad guys in New York,” he recalls. “But I say it’s okay – if you lose it, it’s also one reality.”